It is well-known that pneumatic valve assemblies may be partially disposed within an airway defined by a flowbody to control flow of a fluid (e.g., air) therethrough and thus perform any one of a number of functions (e.g., temperature regulation). Valve assemblies of this type typically comprise a valve (e.g., a butterfly valve) that is coupled by way of a linkage assembly to an actuator. The actuator includes a piston and an actuator housing, which may be fixedly coupled to the flowbody. The piston has a first end coupled to the linkage assembly and translates within the housing to actuate the valve. The extension of the piston relative to the actuator housing may cause the valve to open and thus permit airflow through the flowbody, and the retraction of the piston may cause the valve to close and obstruct airflow; however, it should be appreciated that the valve assembly may instead be configured such that the valve opens and closes with piston retraction and extension, respectively. In fuel actuated valve assemblies (e.g., bleed valve assemblies, control valve assemblies, cooling valve assemblies, etc.), the pressure differential described above may be externally controlled to command valve positioning within the airway.
The movement of the piston within the actuator housing is dictated by the pressure differential between two hydraulic chambers (i.e., a closing chamber and an opening chamber) within the actuator housing and generally defined by the inner surface of the housing. These chambers may be isolated from each other by a cuffed region of the piston that ends radially outward to sealingly engage the inner surface of the housing. When the pressure in the opening chamber exerts a force on the piston greater than that exerted by the pressure in the closing chamber, the piston extends and the valve opens. Conversely, when the pressure in the closing chamber exerts a force on the piston greater than that exerted by the pressure in the opening chamber, the piston retracts and the valve closes. In some valve assemblies, a linear positioning sensor (e.g., a linear variable differential transformer, or LVDT) is disposed within the actuator housing to facilitate monitoring the displacement of the piston therein and establishing the position of the valve plate within the airway. After determining the current position of the piston, a controller may initiate an appropriate adjustment to move the piston to a target position and thereby actuate the valve in a desired manner.
Due in large part to elevated operational temperatures, leakage is a concern in fuel actuated valve assemblies. For this reason, these valve assemblies are routinely provided with redundant, seals to minimize the likelihood of external leakage. Joints produced when multiple sections of the housing are coupled to form the actuator body, for example, must be provided with appropriate sealing assemblies. As a representative example, a known actuator housing is formed by two separate sections: a main actuator housing section, which substantially contains the linear positioning sensor and the piston when the piston is in a retracted position; and a seal retainer section, which allows the piston rod to translate through the housing and contains a portion of the linkage. These sections are bolted together at their interface to form the actuator housing. This mechanical coupling requires an additional flange/bolt assembly and static seals disposed between the main actuator housing section/seal retainer section interface and between the seal retainer section and the piston.
Considering the above, it is not surprising that jointed actuator housings (i.e., actuator housings formed by coupling multiple sections together) result in a valve assembly of increased complexity, cost, size, and weight. Further, the additional seals required by jointed actuator housings provide other sites at which external leakage may occur thus decreasing system reliability and increasing maintenance demands. Further still, due to the stroke force produced by the action of the piston, such housings may experience structural stress at their joints, which may result in increased wear on the seals and an increased likelihood of fuel leakage.
It should thus be appreciated from the above that it would be desirable to provide an improved fuel powered actuator assembly including a unitary housing that reduces the number of requisite joints and seals, and therefore reduces the overall cost, complexity, weight, and size of the assembly. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.